Endocrine Physiology 1 Flashcards
Anatomical location of the principal endocrine glands and tissues of the body
Hypothalamus Pituitary gland Pineal gland Parathyroid glands Thyroud glands Thymus gland Stomach Adrenal galnds Pancreas Kidney Adipose tissue Small Intestine Ovaries Testes
Chemical signaling methods are used by both ___ system and ___ system
Nervous system and Endocrine system
Synaptic is used by
Nervous system only - Ns
Neuroendocrine =
cells that have major features of neurons but release hormones into the blood to affect non neuronal tissue (different organ)
Ex - cells of the hypothalamus that secrete releasing hormones that act on the ant pituitary
Autocrine =
Autoreceptors on nerve cells that respond to a NT released by a cell
Cells secrete chemicals into interstitial fluid that bind to surface receptors of the cell that secreted it (ex - GH)
One cell is right next to the cell and acting on it and it can talk to itself
Paracrine =
Many autonomic synapses onto target cells
Endocrine cells can release hormones into the interstitial fluid that act on nearby cells
Nearby cells!
Endocrine =
Classic meaning of hormone as substance secreted into blood that carries it to the target tissue
True hormones (endocrine secretions) are released by
Ductless galnds and are carried by the bloodstream to their sites of action
Hormones are often classified according to
their chemical structure
Polypeptides with less than 100 amino acids are called
Peptides
Ex - oxytocin
In general polypeptides with more than 100 amino acids are calls
Proteins
Ex - GH
Steroid hormones are derived from
Cholesterol
Amine hormones are derived from
Amino acids
Thyroid hormones are classified as
Amine hormones
But keep in mind that they are different because they contain iodine
Peptide hormones and water
Peptide hormones are water soluble - so they easily enter the circulatory system for transport to their target organs
Steroids are ___ soluble
Lipid
So they are not stored in vesicles
Once they are synthesized, they diffuse across the cell membrane into the interstitial fluid and then the blood
Cortisol, Aldosterone, Testosterone, Estradiol
Amine hormone synthesis - NE and Epinephrine are synthesized in the
adrenal medulla
Derived from tyrosine
Mechanism of action of hormones - hormones have to bind to
their specific receptor on or in their target cell
So - only target cells (those having the hormone receptors for a specific hormone) will respond to that hormone
Mechanism of action of hormones - Water soluble hormones bind to
receptors on the cell membrane
Ex of water soluble = protein, peptide, catecholamine
Mechanism of action of hormones - Lipid soluble hormones bind to
Receptors in the cell cytoplasm or in the cell nucleus
Where do we make proteins and where are they packaged up
Make them in the ER
Package in the golgi
Determining the level of free hormones circulating in the bloodstream - Free hormones equilabrate with
The forms that are bound (inactive) to either receptors or plasma carrier proteins
You want things bound so that they do not filter through the glomerulus
Types of NT receptors
Ligand gated ion channels
G protein coupled receptors
Leptin uses what kind of receptor
Enzyme linked receptor
Receptor for a hormone
Hormones that use it
G protein coupled receptor
Glucagon, Angiotensin, GnRH, SS, GHRH, FSH, LH, TSH, ACTH
Epi, NE (amino acid derived)
Different types of hormone receptors - Intracellular receptors
Can be soluble receptor proteins found in the cytosol or in the nucleus
Ex - thyroid hormone receptor is located in the nucleus where it is bound to DNA and it represses transcription when there is no hormone bound to it
When hormone binds to it, it stimulates transcription of thyroid hormone
Different types of hormone receptors - Steroid receptors
Cannot bind to DNA in the absence of the hormone
Once the steroid binds to its receptor the complex moves into the nucleus where it binds to its specific responsive element on the DNA and initiates transcrition
Different types of hormone receptors - Steroid receptors - examples of hormones that use steroid receptors
Estrogen
Progesterone
Cortisol
Aldosterone
Physiological response driven negative feedback loop example
Say lots of glucose circulating in blood
Goes throughout body and specifically to pancreas
Pancreas (endocrine gland) secretes hormone that then goes to target organ
And then physiological effect of taking up glucose
Gives result of having less circulating glucose
So this is negative feedback to the endocrine gland
Endocrine axis =
Pituitary is the middle of it
Endocrine axis driven negative feedback example
Hypothalamus telling the pituitary what to do
Pituitary to endocrine glands that tells them to release their hormone
Hypothalamus - releasing hormone - pit gland - tropic hormone - endocrine gland - hormone
Tropic hormone =
Acts on another endocrine gland and makes it grow or secrete
Acts on a peripheral gland that makes a hormone
What is the biggest difference with physiological vs. endocrine negative feedback
Physiological - the target organ gives the negative feedback
Endocrine - target organ does not feedback, it is the hormone and/or the pituitary gland providing negative feedback
Types of endocrine axis driven negative feedback
Ultra short loop
Short loop
Long loop
Types of endocrine axis driven feedback - Ultra short loop
when the hypothalamus talks to itself
Endocrine axis loop?
Releasing factor acts on the anterior pituitary that releases a tropic hormone that then acts on the target organ which then releases a hormone
Types of endocrine axis driven feedback - Short loop
Feedback of ant pituitary back onto the hypothalamus
Types of endocrine axis driven feedback - Long loop
Target organ (testosterone) on the hypothalamus (think testicles to hypothalamus - pretty far haha) Even Target organ to anterior pituitary would be long loop too
Types of endocrine axis driven feedback - Complex multi level feedback
A lot of things acting in your bran that impact the hypothalamus
Hypothalamus is either exciting or inhibiting the ant/post pituitary which release hormones that act on the target organs which release their own hormones
Then these can go back and act on the ant/post pituitary
Circadian clock - what is it
Suprachiasmatic nucleus
Hormones throughout the day
It matters when people get their hormone levels checked and what their circadian rhythm is!
What is normal for midnight may be incredibly low for 8am
GH - circadian rhythm
GH is especially powerful during strenuous exercise and also during the first few hours of deep sleep
Hormone degradation - we don’t want hormones in the blood stream forever - we keep them around longer - Steady state concentration
We can control their rate of synthesis
Balance of synthesis and degredation determines the steady state concentration of a hormone
Because of complicated feedback mechanisms of the endocrine system - we can normally inc synthesis enough to compensate for inc degredation
Hormone degradation - we don’t want hormones in the blood stream forever - we keep them around longer - how do we get rid of them?
Liver is the most important site for degredation of most hormones (put them in bile)
Kidney is also important since it can excrete degraded products and sometimes intact hormones
Liver and kidney disease can impact
endocrine function by altering rates of degredation and/or excretion
Various drugs can also alter normal rates of hormone degredation
Median eminence is
In the hypothalamus
Anterior pituitary is located where
under the optic chiasm
Anterior vs. Posterior pituitary size
Anterior is larger
Anterior pituitary AKA
Adenohypophysis
Posterior pituitary AKA
Neurohypophysis
Hypothalamus is located
in the floor and walls of the third ventricle
Part of the diencephalon
Anterior pituitary has a direct vascular link with the
hypothalamus
Posterior pituitary is comprised largely of
Endings of axons of neurons whose cell bodies are in the supraoptic and paraventricular nuclei of the hypothalamus
Posterior pituitary is connected to the
hypothalamus by the hypothalamohypophysial tract
Pituitary is encased in
A tough capsule of dura which is in the bony sella turcica
The area of the hypothalamus where the portal vessels arise is the
median eminence
Primary vascular plexus is in the
hypothalamus with part in the median eminence
other plexus in ant pituitary
Hormone secreting cells of the anterior pituitary gland - Cell types
Somatotrope Lactotrope Corticotrope Thyrotrope Gonadotrope
Hormone secreting cells of the anterior pituitary gland - Cell types - Somatotrope secretes what hormone? And what percentage?
Somatotrope secretes Growth Hormone
50% (the most)
Hormone secreting cells of the anterior pituitary gland - Cell types - Lactotropes secrete what hormone? and what percentage?
Lactotropes secrete prolactin
10-30%
Hormone secreting cells of the anterior pituitary gland - Cell types - Corticotropes secrete what hormone? and what percentage?
ACTH
10%
Hormone secreting cells of the anterior pituitary gland - Cell types - Thyrotrope secretes what hormone and what percentage
TSH
5%
Hormone secreting cells of the anterior pituitary gland - Cell types - Gonadotrope secretes what hormones and what percentage
FSH and LH
20%
